© 1996 Heron Publishing—Victoria, Canada
Survival strategy of hiba (Thujopsis dolabrata var. hondae) and two broad-leaved trees in northern Japan in response to creep and glide pressures of snow
Hiromi Tanabe and Hiromichi Onodera
Snow Influences Laboratory, Tohoku Research Center, Forestry and Forest Products Research Institute, Nabeyashiki 72, Shimokuriyagawa,
Morioka 020-01, Japan / Received March 2, 1995
Summary
We compared the tolerance of hiba (Thujopsis dolabrata var. hondae Makino), beech (Fagus crenata Blume) and oak (Quercus serrata Thunb.) to creep and glide pressures of snow. The top/root (T/R) ratio of hiba trees ranged between 7.1 and 41.4 compared
with 3.6–10.9 and 1.0–12.4 for beech and oak, respectively. However, if prostrate stems bearing adventitious roots were included
in the root component, the T/R ratio of hiba trees was comparable to the range observed for the co-occurring broad-leaved
species (1.2 to 3.9). The adventitious roots originating from the trunks of hiba trees extended horizontally during the early
growth stage. However, when stem diameter at ground level reached 6–7 cm, some large-diameter adventitious roots developed
vertically to form, so-called, sustentacular roots. Because all of the dead hiba trees that we examined lacked sustentacular
roots, we conclude that sustentacular roots are necessary to enable young hiba trees to withstand the pressures of snow movement.
All of the large beech trees formed sustentacular roots and no dead beech trees were observed. Not all the oak trees formed
sustentacular roots, which may explain why this species was found only on gentle slopes.
Keywords:
basal bending, root system development, snow damage, sustentacular roots.
